Telmisartan which is 4′-[2-n-propyl-4-methyl-6-(1-methylbenzimidazol-2-yl) benzimidazol-1-ylmethyl]biphenyl-2-carboxylic acid is an angiotensin-II receptor antagonist used in the treatment of hypertension and other medical indications, either alone or in combination with other therapeutic agents.
Telmisartan, a compound of the structural formula 5, has been synthesized by various methods as described in the prior art.

The synthesis of telmisartan has been described in the prior art by various reaction pathways including reacting 2-n-propyl-4-methyl-6-(1′methylbenzimidazol-2′-yl)benzimidazole with either 4′-bromomethylbiphenyl-2-carboxylic acid alkyl ester or 4′-halomethyl cyano biphenyl, specifically the 4′-bromomethyl derivative.
US20040236113 A1 and US20130137878 A1 relate to a method for the production of telmisartan by reacting 2-n-propyl-4-methyl-6-(1′-methyl-benzimidazol-2′-yl)benzimidazole specifically with 4-bromomethyl-2′-cyanobiphenyl and subsequently conducting hydrolysis of the cyano group to the acid group. This patent does not describe the preparation of 4-chloromethyl-2′-cyanobiphenyl nor the use of this compound for the preparation of telmisartan on a commercial scale. This patent specifically uses the 4-bromomethyl-2′-cyanobiphenyl compound as one of the raw material to obtain telmisartan.
Various research publications have indicated that organic bromine compounds are toxic compared to corresponding chloro derivatives.
Therefore, there is a need for an alternative method of synthesis for the industrial preparation of telmisartan, which overcomes the drawbacks of the processes reported in the prior art and makes use of commercially available or easy to prepare intermediates.